The inventive 1,2,3,4,5,6,7,8-octohydro-9-phenylacetamidoacridine and the hydrochloride thereof are novel compounds and are disclosed for the first time herein. Their structurally similar compound 9-amino-1,2,3,4,5,6,7,8-octohydroacridine has been proved to have an inhibition activity for cholinesterase and thus useful for the treatment of senile dementia (Chinese Patent No: ZL 03104541.3). In addition, U.S. Pat. No. 5,767,126 (Marchbanks and Roger) discloses the polyhydrogenated and dehydrogenated derivatives of 9-amino-1,2,3,4-tetrahydroacridine (Tacrine) which is used for treating senile dementia and has a hepatotoxicity. U.S. Pat. No. 4,942,237 discloses an acridine derivative called ISOXAZOLO (5,4,3-KL) ACRIDINE and its use for the treatment of pains and various memory dysfunctions.